Intake Flow Structure and Swirl Generation in a Four-Valve Heavy-Duty Diesel Engine

Abstract

Intake flow structure was studied using various port geometries in a four-valve heavy-duty diesel engine. Swirl ratio, LDV measurements of bulk flow and turbulence, and flow visualization experiments were conducted on a steady-state bench rig. In addition to the standard production port, archetypal intake port flows (swirl, anti-swirl and tumble) were created using intake valve shrouds. These flow types are not usually found in heavy-duty engines, which typically employ quiescent combustion chamber designs. However, recent CFD analyses have indicated that intake flow structures can significantly influence engine pollutant emissions (Fuchs and Rutland, 1998). Thus, it was of interest to characterize these flows in a heavy-duty engine. The measured swirl and axial velocity components were analyzed to reveal the swirl and tumble generation mechanisms, and the LDV data compared favorably with the swirl meter results. The flow visualization confirmed the existence of flow recirculation regions under the intake valves also seen in the LDV data. These flow structures help to explain the origins of the overall swirl and tumble flow fields. The results were also compared with available CFD predictions made using the same port configurations. The measured swirl levels were found to agree with the CFD trends. However, in some cases quantitative differences were found, presumably due to the effect of piston motion in the actual engine. These differences need to be accounted for when evaluating port designs from steady-flow measurements, especially in cases with high tumble flow components. [S0742-4795(00)00804-8]